412
FXUS62 KMFL 251901
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
301 PM EDT Wed Sep 25 2024

...New LONG TERM...

.SHORT TERM...
(Rest of today through Thursday)
Issued at 133 PM EDT Wed Sep 25 2024

*** KEY POINTS FOR HURRICANE HELENE ***

Impacts for South Florida: Hurricane Helene will bring about
heavy rain, gusty winds, storm surge across the Gulf Coast, and
increased flooding potential as its outer bands move across the
region. A Tropical Storm Warning is in effect for all of South
Florida, including the local waters, until 2AM Friday morning.

Flood Watch Issued: A Flood Watch is in effect for all of South
Florida, as rainfall amounts of 2-6 inches are possible across
inland and metro areas.

Storm Surge Risk: 2-4 feet of storm surge is expected along the Gulf
Coast from Bonita Beach to Flamingo due to Helene`s size and the
shallow Florida shelf. Values as high as 5 feet may be observed. A
Storm Surge Warning is in effect for these coastal areas.

Limited Tornado Threat: Tropical tornado risk is limited but a few
tornadoes may spawn tonight into early Thursday, especially along
the southwest Florida and the Lake Okeechobee region.

***

South Florida is already experiencing the effects of Helene today
as the first few lines of convection have moved across the region.
MFL soundings and ACARS data are showing high precipitable water
(PWAT) values exceeding 2.2 inches, dew points in the upper 70s,
and warm air aloft. Outer bands from Helene will continue to move northward
across the region today, bringing periodic heavy rain with intervals
of sunshine. Winds from the southeast will continue to strengthen
throughout the day, with gusts exceeding 30 mph, especially along
the coasts.

The primary impacts from Helene will arrive late tonight into
early tomorrow morning as the storm center progresses northward
through the Gulf of Mexico. A significant moisture envelope will
move into the region during this time, with PWAT values forecasted
between 2.3 to 2.5 inches - nearing climatological highs for late
September. Models also indicate a long, skinny CAPE profile,
supportive of warm cloud processes and heavy rainfall. Given these
parameters, there is potential for heavy rain and localized
flooding across the area. Rainfall amounts between late Wednesday
and Friday evening are expected to range from 2 to 4 inches
inland, with metro areas potentially seeing 3 to 6 inches.

Additionally, storm surge across portions of southwest Florida may
reach 2-4 feet, with some vulnerable coastal areas possibly
seeing up to 5 feet due to the large size of Helene and the
shallow nature of the Florida shelf. Dangerous marine and boating
conditions will also prevail across the entire region, with the
most significant impacts felt in the Gulf waters. As Helene`s
outer feeder bands move across the region, tropical storm-force
wind gusts will also be possible throughout South Florida, with
sustained winds up to 30 kts and gusts up to 40 kts possible
tomorrow.

Aside from the risks of storm surge, flooding rains, and wind, the
threat of tropical tornadoes appears limited. South Florida`s
residence time within the northeast quadrant of the system could
reduce the window for tornadic activity, with the peak risk for
tornadoes between 18Z-00Z due to dry air mixing and diurnal heating.
Tornado potential may be confined to coastal areas of Collier,
depending on the storm`s track. A second window for possible
tornadogenesis may open in the Lake Okeechobee region Thursday
afternoon as Helene moves further north in the Gulf of Mexico.

Temperatures will remain near climatological norms, as cloud cover
and widespread rain keep highs in check.

&&

.LONG TERM...
(Thursday night through next Tuesday)
Issued at 244 PM EDT Wed Sep 25 2024

Helene will eventually make landfall sometime on Thursday evening
across the Big Bend region of Northern Florida. As the storm
weakens and pushes further off to the northeast on Friday, a
stream of elevated moisture, characterized by PWAT values of
2.3-2.5 inches, will continue to drape over the region as breezy
southwesterly flow persists. This southwest flow, associated with
Helene`s extratropical transition, could enhance low-level
convergence, further elevating hydrologic concerns, especially in
areas prone to poor drainage for the end of the week. The
moisture fetch will likely linger into the weekend, keeping
humidity levels high across South Florida.

Through the weekend, South Florida will experience a transitioning
weather regime. Initially, low-level steering flow will come from
the south and southwest, but it is expected to gradually shift to
the west and northwest over time. The stream of moisture will become
more diffuse, but enough will remain to produce scattered showers
and thunderstorms. Localized flooding may occur, but overall impacts
should be minimal.

Looking beyond the weekend, some long-range models suggest the
potential for a weak frontal passage, bringing a light northwesterly
flow. However, it is too early to confirm this, and the event
remains uncertain given its distance in time.

&&

.AVIATION...
(18Z TAFS)
Issued at 133 PM EDT Wed Sep 25 2024

SCT SHRA/TSRA coverage will gradually increase as the day
progresses and Hurricane Helene enters the SE Gulf of Mexico. SSE
winds 15-20 kts with gusts 25-30 will be possible through the
night and into tomorrow morning, when winds could strengthen up to
25-30 kts sustained and gusts up to 40 kts. Flight restrictions
will be likely again tonight and tomorrow during periods of heavy
rain.

&&

.MARINE...
Issued at 133 PM EDT Wed Sep 25 2024

Moderate easterly winds will gradually increase in magnitude as
Hurricane Helene approaches across the Gulf waters. Winds and
seas will become dangerous across the local waters as the system
intensifies and moves northward alter tonight and tomorrow, with
tropical storm conditions likely across all the local waters as
Helene`s outer bands push across the area. Numerous to widespread
showers and thunderstorms embedded within those outer bands will
generally be observed today and tomorrow.

&&

.BEACHES...
Issued at 133 PM EDT Wed Sep 25 2024

Moderate to major coastal flooding can be expected over the Gulf
coast late tonight into tomorrow as Hurricane Helene strengthens
and tracks through the SE Gulf of Mexico.

Strengthening onshore flow will result in an extended period of high
rip current risk over the east coast (likely through the work week),
with potentially hazardous surf developing over the Palm Beaches in
the mid-week period. Additionally hazardous beach conditions look
likely over the Gulf coast beaches starting Thursday as surf
increases in association with Tropical Storm Helene.

&&

.PRELIMINARY POINT TEMPS/POPS...
Miami            80  90  81  91 /  80  80  70  70
West Kendall     79  91  80  91 /  80  80  70  80
Opa-Locka        80  91  81  92 /  80  80  60  80
Homestead        80  89  80  90 /  80  80  70  70
Fort Lauderdale  79  90  80  90 /  80  70  60  80
N Ft Lauderdale  80  91  80  92 /  80  70  60  80
Pembroke Pines   81  92  81  93 /  80  70  60  80
West Palm Beach  80  91  80  92 /  70  70  60  70
Boca Raton       80  91  80  93 /  80  70  60  70
Naples           79  89  81  89 /  90  90  80  70

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...Tropical Storm Warning for FLZ063-066>075-168-172>174.

     Flood Watch through Friday morning for FLZ063-066>075-168-
     172>174.

     Storm Surge Warning for FLZ069-075.

     High Rip Current Risk through Friday evening for FLZ168-172-173.

     High Surf Advisory until 8 PM EDT Thursday for FLZ168-172-173.

AM...Tropical Storm Warning for AMZ610-630-650-651-670-671.

GM...Tropical Storm Warning for GMZ656-657-676.

&&

$$

SHORT TERM...SRB/ATV
LONG TERM....SRB/CWC
AVIATION...ATV